1. Field of the Invention
This invention relates generally to screen printing equipment and more particularly to an improved stretch frame structure for printing screens.
2. Discussion of the Prior Art
In the printing process commonly known as silk screen printing or silk screening and referred to herein simply as screen printing, an image to be printed is permanently formed on a printing screen by photo-etching or other technique which blocks the screen openings in a way that defines the image. Ink is then forced through the unblocked screen openings onto a printing surface to reproduce the image on the surface. Effective high quality screen printing with good registration and resolution in the finished print requires maintenance of the printing screen in a very taut and stable condition during the printing operation. To this end, the printing screen is supported in a stretch frame or screen chase having means for gripping the edges of the screen and stressing the screen edgewise.
A variety of printing screen stretch frames have been devised. Examples of such stretch frames are described in the following U.S. Pat. Nos.: 3,553,862; 3,908,293; 4,409,749. While these existing stretch frames are quite satisfactory in many respects, they do have at least one common disadvantage. This disadvantage resides in their relatively complex and costly construction involving many different parts which must be machined or otherwise specially fabricated and then assembled into a finished frame structure. Accordingly, there is a definite need for an improved stretch frame structure having a simplified, less costly construction.